BMW 4 Series (2014) is 219 mm (8.62 inch) longer, 29 mm (1.14 inch) wider, 40 kg (88 lbs) lighter and has 40 liters (1.41 ft3) bigger cargo space than Mercedes B-Class (2020).
Mercedes B-Class (2020) is 200 mm (7.87 inch) higher than BMW 4 Series (2014).